GH-73991: Disallow copying directory into itself via pathlib.Path.copy()

Lib/pathlib/_abc.py

@@ -14,6 +14,7 @@
 import functools
 import operator
 import posixpath
+from errno import EINVAL
 from glob import _GlobberBase, _no_recurse_symlinks
 from stat import S_ISDIR, S_ISLNK, S_ISREG, S_ISSOCK, S_ISBLK, S_ISCHR, S_ISFIFO
 from pathlib._os import copyfileobj
@@ -564,14 +565,38 @@ def samefile(self, other_path):
  return (st.st_ino == other_st.st_ino and
  st.st_dev == other_st.st_dev)
 
- def _samefile_safe(self, other_path):
+ def _ensure_different_file(self, other_path):
  """
-Like samefile(), but returns False rather than raising OSError.
+Raise OSError(EINVAL) if both paths refer to the same file.
  """
  try:
- return self.samefile(other_path)
+ if not self.samefile(other_path):
+ return
  except (OSError, ValueError):
- return False
+ return
+ err = OSError(EINVAL, "Source and target are the same file")
+ err.filename = str(self)
+ err.filename2 = str(other_path)
+ raise err
+
+ def _ensure_distinct_path(self, other_path):
+ """
+ Raise OSError(EINVAL) if the other path is within this path.
+ """
+ # Note: there is no straightforward, foolproof algorithm to determine
+ # if one directory is within another (a particularly perverse example
+ # would be a single network share mounted in one location via NFS, and
+ # in another location via CIFS), so we simply checks whether the
+ # other path is lexically equal to, or within, this path.
+ if self == other_path:
+ err = OSError(EINVAL, "Source and target are the same path")
+ elif self in other_path.parents:
+ err = OSError(EINVAL, "Source path is a parent of target path")
+ else:
+ return
+ err.filename = str(self)
+ err.filename2 = str(other_path)
+ raise err
 
  def open(self, mode='r', buffering=-1, encoding=None,
  errors=None, newline=None):
@@ -826,8 +851,7 @@ def _copy_file(self, target):
  """
  Copy the contents of this file to the given target.
  """
- if self._samefile_safe(target):
- raise OSError(f"{self!r} and{target!r} are the same file")
+ self._ensure_different_file(target)
  with self.open('rb') as source_f:
  try:
  with target.open('wb') as target_f:
@@ -847,6 +871,13 @@ def copy(self, target, *, follow_symlinks=True, dirs_exist_ok=False,
  """
  if not isinstance(target, PathBase):
  target = self.with_segments(target)
+ try:
+ self._ensure_distinct_path(target)
+ except OSError as err:
+ if on_error is None:
+ raise
+ on_error(err)
+ return
  stack = [(self, target)]
  while stack:
  src, dst = stack.pop()

Lib/test/test_pathlib/test_pathlib_abc.py

@@ -1501,19 +1501,20 @@ def iterdir(self):
  raise FileNotFoundError(errno.ENOENT, "File not found", path)
 
  def mkdir(self, mode=0o777, parents=False, exist_ok=False):
- path = str(self.resolve())
- if path in self._directories:
+ path = str(self.parent.resolve() / self.name)
+ parent = str(self.parent.resolve())
+ if path in self._directories or path in self._symlinks:
  if exist_ok:
  return
  else:
  raise FileExistsError(errno.EEXIST, "File exists", path)
  try:
  if self.name:
- self._directories[str(self.parent)].add(self.name)
+ self._directories[parent].add(self.name)
  self._directories[path] = set()
  except KeyError:
  if not parents:
- raise FileNotFoundError(errno.ENOENT, "File not found", str(self.parent)) from None
+ raise FileNotFoundError(errno.ENOENT, "File not found", parent) from None
  self.parent.mkdir(parents=True, exist_ok=True)
  self.mkdir(mode, parents=False, exist_ok=exist_ok)
 
@@ -1758,6 +1759,32 @@ def test_copy_symlink_follow_symlinks_false(self):
  self.assertTrue(target.is_symlink())
  self.assertEqual(source.readlink(), target.readlink())
 
+ @needs_symlinks
+ def test_copy_symlink_to_itself(self):
+ base = self.cls(self.base)
+ source = base / 'linkA'
+ self.assertRaises(OSError, source.copy, source)
+
+ @needs_symlinks
+ def test_copy_symlink_to_existing_symlink(self):
+ base = self.cls(self.base)
+ source = base / 'copySource'
+ target = base / 'copyTarget'
+ source.symlink_to(base / 'fileA')
+ target.symlink_to(base / 'dirC')
+ self.assertRaises(OSError, source.copy, target)
+ self.assertRaises(OSError, source.copy, target, follow_symlinks=False)
+
+ @needs_symlinks
+ def test_copy_symlink_to_existing_directory_symlink(self):
+ base = self.cls(self.base)
+ source = base / 'copySource'
+ target = base / 'copyTarget'
+ source.symlink_to(base / 'fileA')
+ target.symlink_to(base / 'dirC')
+ self.assertRaises(OSError, source.copy, target)
+ self.assertRaises(OSError, source.copy, target, follow_symlinks=False)
+
  @needs_symlinks
  def test_copy_directory_symlink_follow_symlinks_false(self):
  base = self.cls(self.base)
@@ -1769,6 +1796,42 @@ def test_copy_directory_symlink_follow_symlinks_false(self):
  self.assertTrue(target.is_symlink())
  self.assertEqual(source.readlink(), target.readlink())
 
+ @needs_symlinks
+ def test_copy_directory_symlink_to_itself(self):
+ base = self.cls(self.base)
+ source = base / 'linkB'
+ self.assertRaises(OSError, source.copy, source)
+ self.assertRaises(OSError, source.copy, source, follow_symlinks=False)
+
+ @needs_symlinks
+ def test_copy_directory_symlink_into_itself(self):
+ base = self.cls(self.base)
+ source = base / 'linkB'
+ target = base / 'linkB' / 'copyB'
+ self.assertRaises(OSError, source.copy, target)
+ self.assertRaises(OSError, source.copy, target, follow_symlinks=False)
+ self.assertFalse(target.exists())
+
+ @needs_symlinks
+ def test_copy_directory_symlink_to_existing_symlink(self):
+ base = self.cls(self.base)
+ source = base / 'copySource'
+ target = base / 'copyTarget'
+ source.symlink_to(base / 'dirC')
+ target.symlink_to(base / 'fileA')
+ self.assertRaises(FileExistsError, source.copy, target)
+ self.assertRaises(FileExistsError, source.copy, target, follow_symlinks=False)
+
+ @needs_symlinks
+ def test_copy_directory_symlink_to_existing_directory_symlink(self):
+ base = self.cls(self.base)
+ source = base / 'copySource'
+ target = base / 'copyTarget'
+ source.symlink_to(base / 'dirC' / 'dirD')
+ target.symlink_to(base / 'dirC')
+ self.assertRaises(FileExistsError, source.copy, target)
+ self.assertRaises(FileExistsError, source.copy, target, follow_symlinks=False)
+
  def test_copy_file_to_existing_file(self):
  base = self.cls(self.base)
  source = base / 'fileA'
@@ -1782,8 +1845,7 @@ def test_copy_file_to_existing_directory(self):
  base = self.cls(self.base)
  source = base / 'fileA'
  target = base / 'dirA'
- with self.assertRaises(OSError):
- source.copy(target)
+ self.assertRaises(OSError, source.copy, target)
 
  @needs_symlinks
  def test_copy_file_to_existing_symlink(self):
@@ -1823,6 +1885,13 @@ def test_copy_file_empty(self):
  self.assertTrue(target.exists())
  self.assertEqual(target.read_bytes(), b'')
 
+ def test_copy_file_to_itself(self):
+ base = self.cls(self.base)
+ source = base / 'empty'
+ source.write_bytes(b'')
+ self.assertRaises(OSError, source.copy, source)
+ self.assertRaises(OSError, source.copy, source, follow_symlinks=False)
+
  def test_copy_dir_simple(self):
  base = self.cls(self.base)
  source = base / 'dirC'
@@ -1909,6 +1978,28 @@ def test_copy_dir_to_existing_directory_dirs_exist_ok(self):
  self.assertTrue(target.joinpath('fileC').read_text(),
  "this is file C\n")
 
+ def test_copy_dir_to_itself(self):
+ base = self.cls(self.base)
+ source = base / 'dirC'
+ self.assertRaises(OSError, source.copy, source)
+ self.assertRaises(OSError, source.copy, source, follow_symlinks=False)
+
+ def test_copy_dir_to_itself_on_error(self):
+ base = self.cls(self.base)
+ source = base / 'dirC'
+ errors = []
+ source.copy(source, on_error=errors.append)
+ self.assertEqual(len(errors), 1)
+ self.assertIsInstance(errors[0], OSError)
+
+ def test_copy_dir_into_itself(self):
+ base = self.cls(self.base)
+ source = base / 'dirC'
+ target = base / 'dirC' / 'dirD' / 'copyC'
+ self.assertRaises(OSError, source.copy, target)
+ self.assertRaises(OSError, source.copy, target, follow_symlinks=False)
+ self.assertFalse(target.exists())
+
  def test_copy_missing_on_error(self):
  base = self.cls(self.base)
  source = base / 'foo'
@@ -2876,8 +2967,12 @@ def readlink(self):
  raise FileNotFoundError(errno.ENOENT, "File not found", path)
 
  def symlink_to(self, target, target_is_directory=False):
- self._directories[str(self.parent)].add(self.name)
- self._symlinks[str(self)] = str(target)
+ path = str(self.parent.resolve() / self.name)
+ parent = str(self.parent.resolve())
+ if path in self._symlinks:
+ raise FileExistsError(errno.EEXIST, "File exists", path)
+ self._directories[parent].add(self.name)
+ self._symlinks[path] = str(target)
 
 
 class DummyPathWithSymlinksTest(DummyPathTest):